This invention relates to electrolytic and electrochemical systems, apparatus and methods in which electrolytic reactions are carried out in an aqueous electrolyte and wherein there is a tendency to produce a gas, at least at the cathode. Specifically, the present invention relates to an improved electrolytic system in which gas which tends to form at one of the electrodes is reacted and removed preferably in the form of an electrolytically non-interfering oxidation-reduction reaction product. Important in the practice of this invention is a Contacogen which is the situs of the oxidation-reduction reaction between the gas tending to form at either electrode and a second gas introduced and brought into contact with the Contacogen to effect a reduction-oxidation reaction of the gas formed at the electrode, or tending to form at the electrode. The Contacogen is preferably in the form of particulate wetproofed material maintained in a static condition, as opposed to percolating or in turbulent movement, and simultaneously contacted by an aqueous media, and the reactants. In this way, the gas, if formed, is effectively eliminated.